System for pumping liquids into and out of tanks



A ril.'l4, 1964 G. F. ARKLESS ETAL 3,128,709

SYSTEM FOR PUMPING LIQUIDS INTO AND OUT OF TANKS Filed June 14, 1962 United States Patent Ofiice 3,128,709 Patented Apr. 14, 1964 3,123,709 SYSTEM FOR PUMPING LHQUIDS INTO AND OUT OF TANKS George F. Arkless and Forrest T. Randell, Cathcart, Glasgow, Scotland, assignors to G. 8; I. Weir Limited, Cathcart, Glasgow, Scotland, 21 company of Great Britain Filed June 14, 1962, Ser. No. 202,414 Claims priority, application Great Britain June 17, 1961 4 @laims. (Cl. 103-5) This invention relates to a system for pumping liquids into and out of storage tanks, for example of liquid carrying cargo ships such as oil tankers.

It is customary, when pumping liquid out of the tank of such a ship, to use cargo pumps located low down in the ship, whereby the pumps can be operated with a positive suction head to obviate the necessity for lifting the liquid to the pumps. The pumps are usually located adjacent to the engine room of the ship and the source of power and are connected by a complex arrangement of pipework to the tanks. Where the engine room is located in the after end of the ship and the tanks are located in the hull forward of the engine room, the lengths of the pipes from the tanks to the pumps are often almost as long as the length of the ship. Also, where provision is made for the ship to carry diflerent liquids in different tanks, means including complex valve arrangements is usually provided for switching over any one of the pumps to a selected tank.

It will be understood that the provision of complex valve arrangements and of long lengths of pipes makes maintenance or/ and repair of the pipes and valves complicated and diflicult.

It is an object of the present invention to provide for pumping liquid from a tank, or tanks, for example, of a liquid-carrying cargo ship, without the necessity for providing long lengths of pipes and complex valve arrangements between a pump or pumps and the tank or tanks.

A system, in one embodiment of the invention, comprises at least one cargo pump intended to be located on the deck of a ship on top of or adjacent to a main tank or tanks into and out of which liquid is to be pumped, an auxiliary tank associated with the pump the suction of which is in communication with the interior of the auxiliary tank, a jet pump intended to be located in or adjacent to the bottom of the main tank or of each main tank, a branch connecting the discharge from the cargo pump to the suction of the jet pump, and a duct so connecting the discharge from the jet pump to the interior of the auxiliary tank that liquid may circulate through the cargo pump, the jet pump, the auxiliary tank and back to the cargo pump.

The auxiliary tank is intended to be located on the deck of the ship and the pump may or may not be of the self-priming type.

The cargo pump may be of the positive displacement or rotor-dynamic type and may be operated by a source of power, such as an electric motor, steam turbine or steam cylinder located on the deck of the ship.

A control valve associated with means sensitive to the level of liquid in the auxiliary tank may be inter calated in the branch from the discharge of the cargo pump.

Preferably, means is provided for filling the main tank or tanks by way of the auxiliary tank, the end of the discharge duct from the jet pump being located in the auxiliary tank at a height above the bottom of said tank such that drainage of liquid through said duct to the jet pump does not cause the level of liquid in said tank to fall below said end of the duct, whereby to ensure that there is sufiicient liquid in the auxiliary tank to provide for priming of the jet pump.

A valve-controlled vent is preferably provided in the auxiliary tank above the associated end of the discharge duct from the jet pump.

A valve-controlled filling line preferably leads to the bottom of the auxiliary tank for filling the main tank or tanks.

The control valve may be in the form of a throttle valve associated with a device, such as a float, located within the auxiliary tank and sensitive to the level of liquid in said tank, said device being arranged, for example, to operate the throttle valve either direct or by way of relay mechanism.

An embodiment of the invention will now be described, merely by way of example, with reference to the accompanying drawing which is a schematic elevation of the system applied to a tank of a liquid-carrying ship.

Referring to the drawing, 1 denotes a vertical spindle cargo pump mounted on the deck 2 of a ship above a main tank 3. 4 denotes an auxiliary tank so located on the deck 2 on which the pump 1 is mounted that the normal height 5 from the surface of liquid 6 in the auxiliary tank 4- to the eye of the first-stage impeller of the pump 1 is suificient to permit the pump 1 to inhale the liquid through a duct 7. 8 denotes a jet pump located in the bottom of the tank 3. The driving liquid nozzle of the jet pump 8 is connected by a branch 9 to the main dis charge line 10 of the pump 1 the branch 9 being fitted with a valve 19. The discharge of the jet pump 8 is connected by a vertical duct 11 leading to the interior of the tank 4 and terminating at a height 12 above the bottom of the tank 4 such that, when valve 19 is closed, drainage of liquid through the duct 11 to the jet pump 8 or through pump 1 does not cause the level of liquid 6 to fall below the upper end of the duct 11 thus leaving suflicient liquid in the auxiliary tank 4 to provide for priming of the system.

A control valve in the form of a throttle valve 13 intercalated in the branch 9 is operatively connected to a device 14, such as a float, sensitive to the level of liquid 6 in the auxiliary tank 4.

A filling line 15 controlled by a valve 16 debouches into and terminates adjacent to the bottom of the tank 4. A vent 17 controlled by a valve 18 is provided near the top of the tank 4 above the level of the upper end of the duct 11, the vent 17 leading into the main tank 3.

In practice, when it is desired to fill the tank 3, the valve 18 in the vent 17, a valve 20 provided in the main discharge line 10 from the pump and valve 19 in the branch 9 are closed and the valve 16 in the line 15 is opened to permit flow of fluid into the tank 4. As the valves 18 and 19 and 20 are closed, the tank is pressurised by liquid entering the tank 4 and liquid is caused to flow down the duct 11 and through the jet pump 8 into the tank 3, the tank 3 being vented to atmosphere as is customary with cargo storage tanks, friction losses in the duct 11 being overcome by the pressure of liquid and rapid filling of the tank 3 being eflected. After the tank 3 has been filled the minimum level to which liquid in the tank 4 can fall is determined by the vertical distance between the upper end of the duct 11 and the bottom of the tank 4, namely, the height 12. The quantity of liquid which remains in the tank 4 is suflicient to prime the system.

Then it is desired to empty the tank 3 and to prime the jet pump 8, the valve 20 on the discharge line 10 and valve 19 on branch 9 are kept closed and the valve 18 is opened, and the pump 1 is started. Valve 19 is taken opened to allow liquid to circulate from the tank 4 through the pump 1, the branch 9, the jet pump 8 and the duct 11 back to the tank 4. As soon as the pump 8 entrains liquid, the level of liquid in the tank 4 starts to rise. The valve 20 is then opened to permit discharge of liquid through the discharge line 10.

At the discharge pressures normally used for discharge of liquid overboard, the ratio of driving liquid to liquid entrained by the jet pump 8 is generally between 1:1 and 1:2. To maintain the liquid level constant in the tank 4, the pump 1 must pump the same quantity of liquid out of the tank 4 as the total discharge of liquid from the pump 8, and one half to two thirds of the liquid passing through the pump 1 will be pumped overboard. When the quantity of liquid being pumped out of the tank 4 is less than the total discharge of the jet pump 8, the level of liquid in the tank 4 will rise. A signal from the device 14 will cause the control valve 13 to close to reduce the flow of driving liquid through the duct 11 to the jet pump 8 the total discharge from which will be reduced and the level of liquid in the tank 4 restored to the desired height from the bottom of the tank 4. The converse will occur should the total discharge from the pump 8 be less than the quantity of liquid being pumped out of the tank 4. The valve 18 is left open during pumping of liquid from the tank 3 so that the pressure on the surface of liquid in the tank 4 will be atmospheric pressure. The vent 17 will serve as an overflow in the event of malfunction of the valve 13 or/ and the device 14.

An advantage of the invention is that the pump 1 is located on the deck 2, and it is not necessary to provide a complex arrangement of pipework and valves between the pump 1 and the tank 3. Also, as the jet pump 8 has no moving parts, it can safely be located in the botorn of the tank 3.

What is claimed is:

1. A system for pumping liquids into and out of a main storage tank, including an auxiliary tank, a pump the suction of which is in communication with the interior of the auxiliary tank, a jet pump located in the main tank adjacent the bottom thereof, a branch connecting the discharge from the pump to the suction of the jet pump, a duct connecting the discharge from the jet pump to the interior of the auxiliary tank whereby liquid may circulate through the pump, the jet pump, the auxiliary tank and back to the pump and means for controlling the flow of liquid through the branch connecting the pump discharge with the jet pump suction, said means comprising a device located within the auxiliary tank and sensitive to the level of liquid in the auxiliary tank, a throttle valve intercalated in the branch connecting the pump discharge with the jet pump, and means operatively connecting the device to the throttle valve to control the flow of liquid through the aforesaid branch.

2. A system as claimed in claim 1, in which a valvecontrolled filling line is provided leading into the bottom of the auxiliary tank for filling the main tank by drainage from the auxiliary tank by way of the discharge duct.

3. A system as claimed in claim 2, in which the end of the discharge duct from the jet pump is located within the auxiliary tank at a height sutficiently above the bottom of the auxiliary tank to ensure that there is sufficient liquid in the auxiliary tank to provide for priming of the jet pump, as drainage of liquid through said duct cannot cause the level of liquid in the auxiliary tank to fall below said end of the duct.

4. A system as claimed in claim 3, in which a valvecontrolled vent is provided in the auxiliary tank at a level above the end of the discharge duct from the jet pump, this vent leading into the main tank.

References Cited in the file of this patent UNITED STATES PATENTS 1,535,697 Suczek Apr. 28, 1925 2,061,013 Wade Nov. 17, 1936 2,409,561 Harris Oct. 15, 1946 2,651,259 Brush Sept. 8, 1953 

1. A SYSTEM FOR PUMPING LIQUIDS INTO AND OUT OF A MAIN STORAGE TANK, INCLUDING AN AUXILIARY TANK, A PUMP THE SUCTION OF WHICH IS IN COMMUNICATION WITH THE INTERIOR OF THE AUXILIARY TANK, A JET PUMP LOCATED IN THE MAIN TANK ADJACENT THE BOTTOM THEREOF, A BRANCH CONNECTING THE DISCHARGE FROM THE PUMP TO THE SUCTION OF THE JET PUMP, A DUCT CONNECTING THE DISCHARGE FROM THE JET PUMP TO THE INTERIOR OF THE AUXILIARY TANK WHEREBY LIQUID MAY CIRCULATE THROUGH THE PUMP, THE JET PUMP, THE AUXILIARY TANK AND BACK TO THE PUMP AND MEANS FOR CONTROLLING THE FLOW OF LIQUID THROUGH THE BRANCH CONNECTING THE PUMP DISCHARGE WITH THE JET PUMP SUCTION, SAID MEANS COMPRISING A DEVICE LOCATED WITHIN THE AUXILIARY TANK AND SENSITIVE TO THE LEVEL OF LIQUID IN THE AUXILIARY TANK, A THROTTLE VALVE INTERCALATED IN THE BRANCH CONNECTING THE PUMP DISCHARGE WITH THE JET PUMP, AND MEANS OPERATIVELY CONNECTING THE DEVICE TO THE THROTTLE VALVE TO CONTROL THE FLOW OF LIQUID THROUGH THE AFORESAID BRANCH. 